In general, an electric vehicle is designed in such a way that motors are rotated using a battery as a power source to drive the wheels, thereby to make the vehicle travel. Moreover, there is described in JP-A-59-10102 and JP-A-62-138002 a type of electric vehicle in which a left wheel and a right wheel are driven by individual motors.
When the left wheel and the right wheel are driven by individual motors, for example, it is possible to control the motors independently of each other so as to make the speed of the left wheel and that of the right wheel different from each other. Such a control provides for improved steering so that the driveability of the electric vehicle can be improved.
With the technology disclosed in the above-referenced publications, however, there is the possibility in some cases that when an abnormality occurs in the rotation of one motor, the vehicle gets into a state in which it is difficult to control it in accordance with the driver's desires. Especially, this problem becomes critical in the case of high speed driving. In a most serious case, the vehicle spins so that the steering gets uncontrollable.